1. Field of the Invention:
The present invention relates to adjustable bases or supports, notably for topometric apparatus, of the type comprising essentially a case opening upwards and, in said case a movable member having a substantially vertical axis, adapted to be secured to the apparatus and bearing on the bottom of the case through a ball of which the centre determines a fixed swivel point of the movable member in relation to said case, a pair of screws for adjusting the verticality of the axis of said movable member, which are disposed in substantially vertical planes perpendicular to each other, the centre of said swivel ball lying on the intersection of said vertical planes, and at least one return spring adapted to urge said movable member in a direction such as to cause said member to tilt in a direction opposite to that obtained by screwing in said screws.
2. Description of the Prior Art.:
An adjustable base or support of this general type is already known, notably through French Pat. No. 1,495,545 to the same Applicant. Although the device described in said French patent provides many advantages in comparison with previously known adjustable bases, notably as far as the rapidity of adjustment of the verticality of the axis of said movable member is concerned since the two adjustment screws operate independently of each other and the adjustments accomplished with one screw do not interfere with the adjustments made with the other screw, this known device is, however, attended by some inconveniences. More precisely, this known device is of a particularly elaborate construction, which is obviously objectionable for a mass production, inasmuch as the component elements of the device must be machined with a relatively high degree of precision. Moreover, as a consequence of substantial frictional contacts, the adjustments suffer from a want of smoothness.